1. Field of Invention
The present invention relates to medical teaching aids, and more particularly to those which demonstrate the physiological effects of brain tumor growth in an analog fashion.
This invention further relates to fluid amplifiers and more particularly to fluid amplifiers using a confined stream of liquid.
2. Prior Art & General Background
Fluid amplifiers using jets of gas whose flow is confined in channels and controlled by other jets are well known. Also known are various types of plethysmographies used in physiological investigations of blood circulation.
In particular, an instrument with continuous but not circulating flow into a chamber containing a gas bubble or which varies the volume by lifting the outer, upper wall is generally known as a "windkessel". In effect, it is a surge chamber.
At present, it is the main way to evaluate circulation pulse physically. Certain models are also used in representing intracranial pressure and in testing devices for measuring intracranial pressure. Such a device is shown in Le Roy's U.S. Pat. No. 4,033,141, which discloses a confined volume filled with a porous medium and containing inflatable sacs for adjusting the intracranial pressure. Since such devices make no provision for a circulating medium, they do not provide even a primitive model of the vertebrate intracranial circulation.
A list of prior patents and publications which may be of interest is presented below:
______________________________________ Patent No. Patentee(s) Issue Date ______________________________________ 4,033,141 LeRoy 01/18/77 4,033,141 Gustafsson 07/05/77 ______________________________________ Publication Title Author(s) Publication Date ______________________________________ "Pulse Amplitude Con- Page, W. R. IEEE Frontiers 1982 trol with Human Brain of Engineering Tumor in Man & Analog" in Health Care (pp. 575-579) "Brain Compression Page, W. R. 39th An. Conf. 1986 Damage Tests" on Engineering Medicine & Biology (p. 383) ______________________________________
3. General, Summary Discussion of the Invention
Detail is included in the exemplary embodiment of the demonstration analog unit of the invention described below, which permits adjustment to include a vide variety of intracranial conditions observed clinically. It is a lumped representation of all the basic properties of vertebrate cranial circulation.
A simplified model of the system can be viewed as a rigid closed container, the volume of which is completely filled by many sacs filled with incompressible fluid, one sac being vented to atmosphere and another being connected to a fluid injection system.
The injection of more incompressible fluid into any sac causes fluid to be displaced from the sac and vented to atmosphere, thus maintaining volume equilibrium. This same action is observed in vertebrates cranial circulation and is the basis of the fluid amplifier unit disclosed.
Although this present invention is described in terms of a preferred embodiment of a medical teaching aid, it should be understood that additional uses of the unit are within the scope of the invention as determined by the claims. For a more complete description of the preferred embodiment of the system of the invention, reference should now be made to the following detailed specification and the accompanying drawing.
Alternate approach or modifications are also considered below.